Much of that outrage was taking place on Twitter, where the hashtag #boycottInstagram was trending early Tuesday. Its most prominent user: the hacker group Anonymous. This got more than 500 retweets in a few hours:

Meanwhile, the online petition organization Change.org — fresh from its victory over a reviled new logo for the University of California — turned its attention to the Instagram debacle. A petition from professional photographer and Instagram fan Jennifer Cox, based in Austin, was gaining traction on the service Tuesday.

"I find these terms abusive," Cox writes. "I am upset that after using Instagram for more than two years I am forced to make a choice between letting them take over the rights to my work or leaving the online community I have grown so fond of.

"But I know now that if these terms become effective, I will leave Instagram without a second thought."

The petition calls on Instagram founder Kevin Systrom to "revise your updated terms and conditions in order to let each user decide if their work can be licensed and used under the conditions you propose."

The real question, of course, is whether the number of users quitting Instagram will be significant enough for Systrom and Facebook to take notice. One indication that it just might be: The Instagram photo export service Instaport appeared to go down at several moments on Tuesday, with a note on its homepage warning of overwhelming traffic.

Meanwhile, there was good news for Yahoo: Its long-maligned purchase, photo service Flickr, which fortuitously enough launched its own Instagram-like app last week, was also a trending topic on Twitter in the U.S.

Are you planning to boycott Instagram, or do you think this will all blow over? Let us know in the comments.

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